Apparatus and process useful in making copper oxide rectifiers



Nov. 15, 1949 w. H. SUTTON APPARATUS AND PROCESS USEFUL IN MAKING COPPEROXIDE RECTIFIERS Filed Nov. 13, 1946 INVENTOR Mfl/Gm H. fwfon.

ATTORNE NMFHHMHULmUFHHHWUr WITNESSES:

Patented Nov. 15, 1949 APPARATUS AND PROCESS USEFUL IN MAKING COPPEROXIDE RECTIFIERS William H. Sutton, Pittsburgh, Pa., assignor toWestinghouse Electric Corporation, East Pittsburgh, Pa., a corporationof Pennsylvania Application November 13, 1946, Serial No. 709,502

2 Claims. (Cl. 175-366) My invention relates to methods for producingcopper oxide rectifiers, and in particular, relates rectifiers of theprior art.

Still another object of my invention is to provide a means forregulating at will the cooling rate applied to copper oxide rectifiersin a heattreating process used in their manufacture.

Still another object of my invention is to provide a copper oxiderectifier having electrical characteristics which are an improvementover those of the prior art.

Other objects of my invention will become apparent upon reading thefollowing description taken in connection with the drawing in whichFigures 1 and 2 are, respectively, a sectional view in front elevationand a sectional view in side elevation of an apparatus adapted to carryout the preferred process involved in my invention.

Substantially all processes for manufacturing copper oxide rectifiers atpresent in use are modifications of that described in Grondahl Patent1,840,335, assigned to the Union Switch 8; Signal Company of Swissvale,Pennsylvania, and involve the steps of oxidizing copper at a temperaturejust below its melting point, annealing it at an intermediatetemperature for a moderate period and then cooling it rather rapidly toroom temperature. In most factory production processes. the copper unitshave been cooled from the annealing temperature by dropping them into awater bath. I have found that units subjected to this treatment have adesirably high conductivity to current fiow in the forward, or normallyconductive direction, but that they have only a moderate ability towithstand voltages impressed on them in the inverse, or normallynon-conductive direction. In their service as rectifiers, such unitshave, of course, to withstand inverse voltage equal roughly to twice thepeak voltage of the alternating current supply to which they areconnected, and hence ability to withstand a higher inverse voltage wouldbe a desirable characteristic inasmuch as it would increase the volt- 2age rating of a rectifier oi a given size. Likewise, high conductivityin the forward direction is desirable inasmuch as it limits the powerloss and heating which determine the current rating of a' rectifier of agiven size.

I have found that if, after annealing, the cop- Per units be cooled moreslowly, for example by allowing them merely to stand in the air of theroom instead of plunging them in a water bath, the inverse voltage whichthey are capable of withstanding is very greatly increased but,unfortunately, the conductivity to current in the forward direction isgreatly decreased. Theresuit is that while units subjected to thisslower cooling method are superior for high-voltage lowcurrent service,they offer little or no advantage for many types of service in whichlarger current outputs are desirable.

However, I have discovered that if the rate of cooling is madeintermediate between the rapid water quench, and the slow air coolingabove described, a range is found in which the ability to withstandinverse voltage is substantially as great as that of the more slowlycooled units, while the conductivity in the forward direction issubstantially greater than that of such units, and is in fact onlyslightly smaller than that of units subjected to water quench.

I have accordingly provided a method andapparatus for conducting thecooling of rectifier units from annealing temperature to roomtemperature at a rate which can be predetermined at will. While theprinciples of my invention are applicable in ways readily evident tothose skilled in the art to copper oxide rectifiers of any geometricform, I am illustrating it as applied to rectifiers made in the form ofrectangular copper plates oxidized on substantially their entiresurface. Plate rectifiers of this type are now very widely used in theart, particularly for higher current services, but the modifications ofthe apparatus I show suitable to operate upon another widely used formof rectifier, namely, the circular disc or washer type, will be tooreadily apparent to those skilled in the art to require separateillustration.

Referring in detail to Figures 1 and 2, rectangular copper plates I' maybe suitably supported in spaced relation on rods 2, and oxidized byheating them to temperatures not far below the melting point of copperin a suitable furnace of any type well known in the art (not shown).Upon removal from the furnace, they may be maintained in a suitableannealing environment for a proper annealing period, and then removedand transferr d. to the cooling apparatus shown in Figures 1 and 2. Therods 2 may be supported on hook-members 3 which may be hung on rods 4 ofthe apparatus I show. The rods 4 are supported on projecting arms 5 fromthe links of a conveyor chain running over sprockets 6 and I supportedby bearings (not shown) on shafts 8 and 9 which are preferably in thesame vertical plane. The shaft 8 may be driven at a suitable speed byany desirable arrangement such as theshaft ll of a variable speed motor[2, the rate of rotation of which may be adjusted in accordance with thesystems well known in the art by a variable resistor I-3.

The arms 5 are located at such intervals along the conveyor chains thatthey are spaced further apart than the length of the rectifier plates I.Since I find that a relatively slow movement of the conveyor chainssuffices to produce the desired results with the rectifiers worked upon,it is possible to hang the hooks 3 on the rods 4 during the time thatthe latter are passing in a downward direction, and it is also possibleto remove the hooks 3 from the rods 4 during the time that the brackets5 are moving in an upward direction in the course of movement of theconveyor chains. Thus, in continuous succession, the downward-movingportion of the chain conveyor is loaded with rectifier plates to .becooled, and the cooled plates are continuously removed from theupward-moving portion of the conveyor after cooling.

The substantial cooling of the rectifier plates is carried out byallowing them to be slowly immersed in water or other suitable coolingliquid contained in a tank suitably supported, by means not shown, withthe surface of the liquid preferably below the lower edge of thesprockets 1.-

tank l5; and this temperature may obviously be determined at will bysuitably circulating such liquid through a temperature-determining sysofrectifier plate which has been standardized in commercial manufactureand having the dimensions 12 inches by 4% inches by mils thick, theoptimum ratio of inverse voltage rating to load current is attained whenthe speed of the conveyor chain is from two to three feet per minute.

I claim as my invention:

, 1. The method of manufacturing copper oxide rectifier plates which areabout 12" long by 4%" wide by 50 mils thick which comprises the step ofcooling them from the annealing temperature to about room temperature bymoving them with their longer axis vertical downward into a quenchingliquid at a rate of about two to three feet per minute.

2. Apparatus for cooling copper oxide rectifiers having the form ofplates about 12" by 4%,"in size .which comprises means for supportingsaid plates with their planes vertical, and means for moving said plateswhile supported in said position downward into a quenching bath at arate of about two to three feet per minute.

WILLIAM H. SUTTON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,416,811 Frayer et al May 23,1922 2,070,644 Becker Feb. 16, 1937 2,276,647 Conrad et al. Mar. 17,1942 2,369,565 Haase Feb. 13, 1945

